Scale a recipe
Adjust the amounts to the number of people you want: paste the ingredients, set the original servings and the ones you need, and get the recalculated quantities.
Only the first number on each line (the quantity) is recalculated. Still, double-check cooking times and temperatures, which should not be scaled.
How it works
The tool computes a factor by dividing the servings you want by the recipe's servings, then multiplies
the quantity at the start of each line by that factor. It handles whole numbers, decimals
(e.g. 1.5) and fractions (e.g. 1/2 or 1 1/2).
Tip
Some ingredients don't scale perfectly linearly: yeast, salt, spices and aromatics often need to be dosed «to taste» when you change the amounts a lot. And remember that cooking times and temperatures usually stay the same: change the tin size instead.
What does not scale linearly
Multiplying everything by two works for flour, water, sugar and fats; it does not work for yeast, salt, spices and flavourings. Doubled yeast in a doubled dough makes it rise too fast and leaves an aftertaste; doubled spices bury everything else.
The practical rule is to go up by about half again where you would want to double, and taste. It applies to garlic, chilli and spirits too: these are ingredients perceived non-linearly, so a double quantity reads as far more than double.
Times and temperatures do not double
A doubled cake does not bake in double the time, nor in the same time: it depends on how thick the batter is. If you double the quantity while keeping the same tin, baking takes considerably longer and the temperature has to drop by ten or twenty degrees, otherwise the outside burns and the inside stays raw.
The safest solution is to keep the thickness and change the surface: two tins instead of one, or a tin with double the area. With the thickness unchanged, time and temperature stay those of the original recipe, which is the one thing the arithmetic cannot tell you.
Your pans are the real limit
Doubling ingredients in a pan with no room changes the result more than the recipe does: vegetables in an overcrowded pan boil instead of browning, and a risotto in a narrow pot does not evaporate. These are differences of cooking, not of quantities.
For the same reason halving has its own problems: half an egg does not exist (you beat the whole egg and weigh half), and in a large pan a small quantity dries out. Below a certain amount it is better to make the full recipe and keep the rest.
Nearby tools
For quantities based on the number of guests there is Portions per person, and for changing tin Cake portions. Imperial units are converted with Kitchen measurements.